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Monitoring a marine ecosystem in introductory chemistry

Monitoring a marine ecosystem in introductory chemistry. Rachel Narehood Austin ACS Meeting Boston August 2002. CHEM 107 “Atomic and molecular structure” CHEM 108 “Chemical Reactivity”. CHEM 107b “Chemical Structure and its importance in the environment”

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Monitoring a marine ecosystem in introductory chemistry

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  1. Monitoring a marine ecosystem in introductory chemistry Rachel Narehood Austin ACS Meeting Boston August 2002

  2. CHEM 107 “Atomic and molecular structure” CHEM 108 “Chemical Reactivity” CHEM 107b “Chemical Structure and its importance in the environment” CHEM 108b “Chemical Reactivity in environmental systems” Context for change: Introduce new intro chem sequence (CHEM 107b/CHEM 108b)

  3. CHEM 108b “Chemical Reactivity in Environmental Systems” N2 Basic principles • Using biogeochemical cycles to teach chemistry • Nitrogen cycle: thermodynamics • Carbon cycle: equilibria (including solubility and acid base) • Sulfur cycle: redox chemistry • Oxygen: kinetics

  4. Logistics • 60 students – 3 sections of 20 • 125 gallon salt water aquarium w/UV sterilizer, acrylic tank, sump, ballasts with actinic and lanthanide bulbs on timers, submersible heater, venturi protein skimmer • 11 weeks of lab • Week 1: intro to excel, Beer’s law refresher • Week 2: technical training • Weeks 3,4, & 5: rotation 1 • Weeks 6, 7, & 8: rotation 2 • Weeks 9, 10, & 11: rotation 3 Modified from Ken Hughes – Analytical chemistry

  5. Lab Structure • Group tasks • Nitrogen cycle (NH3, NO2-, NO3-) • Minerals • Alkalinity, pH, [O2(aq)] • Weekly cycle • Week 1: calibration curve + data point • Week 2: data point • Week 3: data point + quality control test

  6. O H M n S O O H 4 NH + HOCl + 3 Methods • PO43- + (NH4)6Mo7O24 [Mo12O36(PO4)]3- + 3 NH4+ [Mo12O36(PO4)]3- + SnCl2Molybdenum Blue (l 690) • NO2- + sulfanilamide + N-(1-napthyl)-ethyelendiamine dihydrochloride (NED dihydrochloride) azo dye(l 543) O N (l 630) Indophenol Standard Methods for the Examination of Water and Wastewater 20th Ed

  7. Methods • Dissolved oxygen (Winkler method) 4 Mn(OH)­2 + O2 + 2 H2O  4 Mn(OH)3 4Mn(OH)3 + 4 I- + 12 H+4 Mn2+ + 2I2 + 12 H2O 2Starch-I­2 + 4 S2O32- 4 I- + 2S4O62- Standard Methods for the Examination of Water and Wastewater 20th Ed

  8. Methods • UV determination of NO3- coupled to IC determination (l=220)

  9. Chemical Concentration Volume Waste Location MnSO4*.H2O 0.05% Amount Disposed DRAIN Lab Manual • Detailed procedures given • Students are encouraged to check other sources • Detailed procedures for hazardous waste • Minimal background (refs. on reserve) Natural Reef Aquariums , by Tullock, ISBN 1-890087-01-7 The Conscientious Marine Aquarist, by Fenner, ISBN 1-890087-02-5 The New Marine Aquarium, by Paletta, ISBN 1-890087-52-1 • Several appendices •  General Technical Comments (units, concentration/dilution, beers law, titrations, pipetters, quadratic equations)

  10. Selected Data Student data facilitates detailed monitoring of tank Variability is large between groups

  11. Assessment • Required sections (10-15 pages, one per group) • Abstract • Introduction • Experimental Section • Results. • Discussion and Conclusion • Grading • Each lab 100 points - 10 points: title/signatures; abstract; intro; exp.; results; discussion, graphs/data presentation; writing/typos; effort • Peer review of rough draft (each student does one per semester) • Final grade 90% lab grade, 10% effort – individual assessment, group assessment, peer review, my assessment

  12. Acknowledgements • Lab development: Ken Hughes, Michael Danahy, Lorna Clark, Gary Starzynski, Kathy Covert, • Images: Hilary Domush, Brent Mann, Dana DiGiando, Elizabeth Lewis, Gary Starzynski • Funding: NSF (CCLI), NSF (Molecular Sciences Institute), Bates College (faculty development funds), Bates College/AACU (SENCER development funds), Kroepsch Teaching Award

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